System Inspection

Engine Control
P0420 Catalyst System Efficiency below Threshold (Bank 1) - System Inspection

Exhaust System Inspection

1. Visually/physically inspect the following conditions :
A. Exhaust system between HO2S and Three way catalyst for air leakage.
B. Damage, and for loose or missing hardware:
2. Was a problem found in any of the above areas?
YES
> Repair as necessary and go to "Verification of Vehicle Repair" procedure.
NO
> Go to "Rear HO2S Inspection " procedure.

Rear HO2S Inspection
1. Visually/physically inspect the rear HO2S for the following conditions:
A. Ensure that the HO2S is securely installed.(Pigtail and wiring harness not making contact with the exhaust pipe)
B. Check for corrosion on terminals.
C. Check for terminal tension. (at the HO2S and at the PCM)
D. Any road damage.
2. Was a problem found in any of the above areas?
YES
> Repair as necessary and go to "Verification of Vehicle Repair" procedure.
NO
> Go to "TWC Inspection " procedure.

TWC Inspection
1. Visually/physically inspect the three-way catalyst(TWC) converter for the following damage:
A. Severe discoloration caused by excessive temperature.
B. Dents and holes.
C. Internal rattle caused by a damaged catalyst.
2. Also, ensure that the TWC is a proper original equipment manufacturer part.
3. Was a problem found?
YES
> Replace TWC and go to "Verification of Vehicle Repair" procedure.
NO
> Check for poor connection between PCM and component: backed out terminal, improper mating, broken locks or poor terminal to wire connection. Repair as necessary and go to "Verification Vehicle Repair" procedure.